Spontaneous and cytokine regulated c-fos gene expression in rheumatoid synovial cells: resistance to cytokine stimulation when the c-fos gene is overexpressed

Reciprocal Feedback Between miR-181a and E2/ERα in Myometrium Enhances Inflammation Leading to Labor

CONTEXT

The initiation of term and preterm labor is associated with an up-regulated inflammatory response in myometrium; however, the underlying signaling pathways remain incompletely defined.

OBJECTIVE

To define the regulatory mechanisms that mediate the increased myometrial inflammatory response leading to labor, we investigated the roles of microRNAs (miRNA/miR).

DESIGN AND SETTING

Human myometrial tissues, isolated smooth muscle cells, and animal models were used to study miR-181a regulation of uterine inflammatory pathways and contractility.

PATIENTS

Myometrial tissues from 15 term pregnant women undergoing elective cesarean section (not in labor) and 10 term pregnant women undergoing emergency cesarean section (in labor) were used.

RESULTS

Expression of the highly conserved microRNA, miR-181a, was significantly decreased in mouse and human myometrium during late gestation. By contrast, the putative miR-181a targets, TNF-α, and estrogen receptor (ER)-α, and the validated target, c-Fos, key factors in the inflammatory response leading to parturition, were coordinately up-regulated. In studies using human myometrial cells, overexpression of miR-181a mimics repressed basal as well as IL-1β-induced TNF-α, C-C motif chemokine ligand 2 and 8 expression, whereas the expression of the antiinflammatory cytokine, IL-10, was increased. Overexpression of miR-181a dramatically inhibited both spontaneous and IL-1β-induced contraction of human myometrial cells. Notably, miR-181a directly targeted ERα and decreased its expression, whereas estradiol-17β reciprocally inhibited expression of mature miR-181a in myometrial cells.

CONCLUSIONS

Thus, increased estradiol-17β/ERα signaling in myometrium near term inhibits miR-181a, resulting in a further increase in ERα and proinflammatory signaling. This escalating feedback loop provides novel targets and therapeutic strategies for the prevention of preterm labor and its consequences.

Microarray profiling of lymphocytes in internal diseases with an altered immune response: potential and methodology

Recently it has become possible to investigate expression of all human genes with microarray technique. The authors provide arguments to consider peripheral white blood cells and in particular lymphocytes as a model for the investigation of pathophysiology of asthma, RA, and SLE diseases in which inflammation is a major component. Lymphocytes are an alternative to tissue biopsies that are most often difficult to collect systematically. Lymphocytes express more than 75% of the human genome, and, being an important part of the immune system, they play a central role in the pathogenesis of asthma, RA, and SLE. Here we review alterations of gene expression in lymphocytes and methodological aspects of the microarray technique in these diseases. Lymphocytic genes may become activated because of a general nonspecific versus disease-specific mechanism. The authors suppose that in these diseases microarray profiles of gene expression in lymphocytes can be disease specific, rather than inflammation specific. Some potentials and pitfalls of the array technologies are discussed. Optimal clinical designs aimed to identify disease-specific genes are proposed. Lymphocytes can be explored for research, diagnostic, and possible treatment purposes in these diseases, but their precise value should be clarified in future investigation.

p21waf1/cip1 is down-regulated in conjunction with up-regulation of c-Fos in the lymphocytes of rheumatoid arthritis patients

Features characteristic to rheumatoid arthritis (RA) including synovial overgrowth and joint destruction are experimentally produced by augmenting c-fos gene expression. We show that cyclin dependent kinase inhibitor p21waf1/cip1, that inhibits cell proliferation, is down-regulated in conjunction with up-regulation of c-fos in the lymphocytes of patients with RA. As to the mechanism of down-regulation of p21waf1/cip1 gene expression, transfection studies in U937 cells showed that c-fos down-regulated phosphorylation and dimerization of signal transducers and activators of transcription (STAT) 1, thereby inhibiting interferon -induced transactivation of p21waf1/cip1. Phosphorylation of STAT1 was indeed decreased in the lymphocytes of patients with RA. Thus, under overexpression of c-fos gene, c-Fos inactivates STAT1 to down-regulate p21waf1/cip1 gene expression in the lymphocytes of patients with RA, and in this way may enhance proliferation of lymphocytes.

Isolation and characterization of rheumatoid arthritis synovial fibroblasts from primary culture--primary culture cells markedly differ from fourth-passage cells

To reduce culture artifacts by conventional repeated passaging and long-term culture in vitro, the isolation of synovial fibroblasts (SFB) was attempted from rheumatoid arthritis (RA) synovial membranes by trypsin/collagenase digest, short-term in vitro adherence (7 days), and negative isolation using magnetobead-coupled anti-CD14 monoclonal antibodies. This method yielded highly enriched SFB (85% prolyl-4-hydroxylase+/74% Thy-1/CD90+ cells; <2% contaminating macrophages; <1% leukocytes/endothelial cells) that, in comparison with conventional fourth-passage RA-SFB, showed a markedly different phenotype and significantly lower proliferation rates upon stimulation with platelet-derived growth factor and IL-1beta. This isolation method is simple and reliable, and may yield cells with features closer to the in vivo configuration of RA-SFB by avoiding extended in vitro culture.